Nozzle stop valve



May 1,1928. 1,668,128

' J. RUTHS NOZZLE STOP VALVE Filed July s, 1922 s sheets-snee*b 1 1 6 od igf J- May l, 1928,-

J. RUTHs NozzLE sToP VALVE Filed July 1922 3 Sheets-Sheet 2 May 1,1-928.

5 Sheets-Sheet 3 '.1. RUTHs 4NOZZLE STOP VALVE Filldu Patented May 1,1928.

UNITED STATES PATENT. OFFICE.

JOHANNES Burns, or nJUnsnoLM, SWEDEN, AssIeNoa To AETIEBOLAGET varon-AcxUMULA'roa, or srocxnoLM, SWEDEN, A coaroaArIoN. l

The stop valves, for instance the usual if the pressure is somewhataltered on either side or on both sides of the valve, this will have avery great influence on the quantity of steam :flowing through thevalve. Assuming for instance that in' a conduit there prevails apressure of l0 atm. before the valve and one of 9 atm. behind the same,then, if for some reason or other the pressure behind the valve shouldrise to 9.5 atm. the rate of iiow through the;valve would be so manytimes less as -1 is less than the square root of 2, i. e. it would beabout per cent smaller. Again, if the pressure behind the valve shouldrise up to 9.8 atm., qthe rate of flow would be reduced by about percent. If the rate of flow through the conduit is tol be kept constant ornearly constant, it is evident that, even if the said pressures vary,the opening of the valve must be constantly regulated according to thevariations in the pressures. Further, in a plant fitted with suchvalves, there 'are some more draw-` backs, mentioned below, vwhichdrawbacks will be described with reference tojFig. l of theiaccompanyingdrawing.

In the drawings, Fig. l is a diagrammatic view of a system using theimproved nozzle stop valve;

Fig. 2is a' graphic comparison of the reu sults obtained by the usualvalve and by the improved valve;

Fig. 3 is a section through one form of the nozzle stop valve;

Figs. 4 to 10 are sections throughm'odllications of the nozzle stopvalve.

Fig. 1 shows a main steam or gas pipe line .1 to which are connectedseveral branch pipes 2f?) and 4. These pipes conduct the steam toconsumers consisting for instance in digesters, boiling vats 5. dryersand the like. In the said branch pipes arel inserted valves 6, assumedto be ordinary-disc stop valves. It is further assumed)that a pres-NOZZLE STOP VALVE.

Application led July 3, 1922, SeralNo. 572,654, and in Sweden J'une 18,1921.v

sure of 10 atm. prevails in the main pipe 1 and that a'pressure of 9atm. is to bemaintained behind the valve 6 in the pipes 2, 3

and 4. Now, if for any reason the pressure in pipe 2 behind the valve 6should rise for example to 9.5 atm., the rate of flow through 6 to thispipe 2 would be about 30 per centincreased as the difference in pressurebefore and-behind these valves is now greater than .b efore, whichcircumstance, in turn, necessltates a readJustment also of valvesinserted in other pipes, in that the rise of pressure in 1 reacts on therate of flow through them. The present invention consists in anadjustable valve so disposed that therate of flow therethrough isindependent of the dilerence in the pressures on the inlet and outletside thereof. That is to say, the rate of the flow through the valve isproportional to the height of pressure at its inlet and to the area ofthe cross section of the paage of the valve. f

Even vfairly greatvariations in the pressure before the valve at itsinlet have only a very small influence on the. rate of flow.therethrough, as will be' shownin the following example i It is assumed,as above, that the pressure before the valve is 10 atm. and the pressurebehind it 9.5 atm. .Now, if for any-reason the pressure before the valveshould rise to which, ifa common valve is used, would mean that the rateof' flow therethrough would be so many times greater as the square ,rootof 2 is greater .than 1, i. e. would be increased by 41 per cent. If, onthe other hand, a valve according to the present inf vention is used, bywhich the rate of flow, asmentioned above, is only dependent on thepressure before the valve and is propory10.5 atm. the difference in thepressure on both sides of the valve will be doubled,`-

tional to the amount of this pressure, the

rate of flow will only be increased -by about per cent. l c

With the aid ofa valve accordin to thls invention it will beI possibleto a apt the supply of steam "to cach consumer toexactly 'suit thedemand. This is of considerable value inl all manufacturingprocesseswhere steam is' used for drying andl boiling pur-l poses, as amore even and superior quality of the product-may be attained thereby.

In such manufacturing processes where ther pressure in the steamconsuming apparatus rises as steam is supplied during the V valves, itnearly always happens that if the loA steam supply to any steam consumeris ncreased or reduced, the operation of all the other steam consumersconnected to the same steam supply pipe, will be considerably disturbed.This drawback is eliminated by the invention.

Preferably the invention consists in a valve shaped as a de Lavalnozzle,through which the steam has to pass. The invention is illustrated inFigs. 2-10. Fig. 2 .is a diagram showing the amount of steam passingthrough a valve of the common type, as well as through a valve.according to the in` vention, under different conditions of pressurebefore and behind the valve.

Figs. 3-5 show non-balanced valves, whereas Figs. 6*-1'0 representembodiments of balanced valves, constructed in accordance with theinvention.

With the aid of Fig. 2, the principle of the present invention will bemore fully explained. Y

One of the fundamental equations for flow of gas through an orifice is:

.in D :F2 C2 y V2 where D is the rate of fiow 'through the nozzle.

F2 is the cross-sectional area of the orifice, C2 is the velocity of thegas fiowing through the orifice, and V, is the specific volume of thegas when leaving the orifice.

The velocity (l2 is dependent on the difference between pressure p,before the orifice' and-the pressure p2 behind the orifice.

The specific volumne V.. is also dependent on p, and p2 wherefore 973may be written 2 as a function of p1, p2 so that ffyfotp.)

- Taking a given value 'fof p'and allowing p, to drop from this value todifferent lower values andnoting the value of the function f( p1, p2)vit can be'determined that the value of the function increaseswithdecrease of 12 very quickly at first, but mpre slowly as g3=0- 57for saturated steam and g3=0. 53 for superheated steam.

If the pressure behind the orifice falls below values with relation top1 as determined by the above ratios, for example if p2.

is less than 0.53 p, the rate of flow through the orifice will beconstant. A further drop lof p2 will not increase the flow. The ratiogivmg maximum rate of flow is called critical ratio and thecorresponding velocity is known as critical velocity.

Above the critical ratio the amount of 'steam flowing through theorifice is dependent on both factors of pressure, both behind and beforethe orifice.

In Fig. 2 curve I shows the relation determined bythe flow function andthev maxi-- mum ratio with respect to superheated steam.

The abscissa represent values of zg and ordinates the steam flow. Takingp, as unity, it is to be seen that for values above 0.53 the rate offlow is dependent on the value of p2.

Practically all valves which serve vto ass steam from one conduit toanother, fol owing the lawsV of the orifice as above set out, allowpassage ofsteam dependent onl changes lof back pressure since theyusually operate on pressure differences with ratios above 0.53.Obviously itvwould be a poor arrangement where a drop of pressure of ormore occurs in a` valve as the power in the. drop of pressure is thenunused.

, Now, on the other hand, the values of p, less than 0.53 p, are used veeffectively in turbines because the intent t ere is to produce velocityyof steam. This is done by means of a gradually expanding nozzle. Such anozzle has a minimum cross-section vat the beginning, and graduallyexpands.

The expansion must be such that decomposition of the jet is avoided.

The above stated equation;

D =F 2 l v 3 2v2 a SO applies in this case with reference to the outletcross section. Taking into account the smallest cross section Fm, thefollowing is found to be the equation for nozzles:

v The ratio of divergence of the nozzle then comes in as a factor. Nowturbine work has lshown that the ratio of divergence isl greater.thegreater the difference between p2 and p1 and that this ratiodecreases as p2 approaches function, that is of rate offiow will be beobtained by use of a valve with a diverg-- 1,eos,1as

of the initial maximum exlt velocity is obtained 'from nozzles ofuniform cross-section or with sides convergent. The divergence ofnozzles has, for the higher ratios, been thought to be'of no use. Ifvelocity is' to'be' lb obtained,'divergence is then a hindrance.

The present invention-relates to thefeld of pressure ratios higher than0.53 in which expanding nozzles have not previously been used and inwhich throttling valves have been used of such construction that flow isdependent upon initial as well as final pressure.

A study of this field has shown that the effect represented by curveII-of Fig. 2 'can ing nozzle for the field betweenpressure ratios 0.53and almost 1.00 in contrast to the straight or convergent nozzles usedfor expanslon. f

This is evident since the last above equation shows that the effectproduced can' beI obtained by multiplying values of curveFI idly towardthe maximum value represented of Fig. 2 by the ratio ofdivergence by theupper horizontalv line which is determined bfy the critical ratio. Thegreater the ratio o divergence, the greater are the values.

The present invention therefore provides the new result Within the fieldof pressure ratios between 0.53 and, for example, 0.97

that the flow of steam through a valve may be made independent of backpressure. The structure involved approachesin some hases the diverg'ing`de Laval nozzle used 1n the field between 0 and 0.53 wherefore the valveherein is giventhat name in description.

Fig. 3 is a diagrammatic representation of a valve structure forcarrying out the present invention.

7 is the valvebody of the de Laval nozzle type 8 is a tapered pin fixedto the valve splndle 9 which affects the adjustment of the throat of thede Laval nozzle,"witl1out affecting its nozzle action and which,consequently, also renders possible' an adjustment of the desired rateof fiow. V

As the rate of flow through the valve, as has been pointed out above, isproportional to the pressure before the kvalve and to the cross sectionthereof, and as the variations in pressure before the valve have only asmall influence on the rate of flow, the latter will thus be practicallydependent only on the.crosssect1onal area of passage, i. e. on thedifferent positions of the tapered pin 8 in relation to the throat ofthe valve body 7.

To make it possible to read off the area ofpassage and the rate of thesteam flow vrespectlvely, the valve spindle 9 is provided with agraduated scale 10 made so as to facilitate a direct or indirect readingthereon of the rate of fiow through the valve. The valve is actuated asusual with a hand wheel 11. To attain an absolutely tight fit againstthe leakage of steam on the valve eing entirely closed, Vthe pin 8 isfitted with a shoulder 12 shaped likea valve disc closing up against theseat 13. As will be seen from the figure, the valve above described isof a straight type. y

Evidently, the valve may be modified and' vadapted in different ways.

Figure 4 shows a valve of angular type,

i. e. for beingr inserted between two pipe lines disposed at rightangles to each other. In a valve of. this latter'type, the graduatedscale is shaped like a disc 14. fixed to the spindle 9. This discrevolves in a slot 15 provided in a slide 16 and brings this slide alongwith it when the hand wheel 11 is turned.

By graduating the slide 16 as well as the disc 14 it will be possible toeffect a very ac.-

curate adjustment of the position of the spindle or the tapered pinrespectively, that is to say of the effective area. of thethroat.

Thus it will be possible to ,very accurately adjust or readoff the rateofthe fiow of steam through the valve.

Fig. 5 shows an embodiment in which the valve seats are shaped so that anozzle 'action will be produced. f

However, the valves according to the vabove-mentioned embodiments arenot balanced, and, consequently, difficulties may. be encountered inoperating same, particularly at high steam pressures and with largevalve dimensions. For example, if the valve is to be used as aregulating member. actuated for instance by a speed governor or thelike,

this is often not feasible by reason of the valve being non-balanced. l

Therefore. some embodiments of the in? vention will be describedhereinbelow, in which embodiments the said 'drawbacks have been avoidedby the valve being made as a balanced one. f

InFig. 6, an insertion piece 17 is arranged inthe valve casing` the saidinsertion piece 17 being provided with circular passage yopenings shapedas de Laval nozzles. Ar-

ranged in this insertion piece before the passage openings is'a movableplunger, slide or the like 18. y'llhisplunger is connected with thespindle 9 which is provided With a thread, by reason of which it isdisplaceable in the longitudinal direction thereof by turning the handWheel 11 and the nut 19. Moreover, the spindle is `provided, inaccordance with the above description with reference to Fig. 3, with agraduated scale 10. The insertion piece 17 is constructed so as to havethe nut 19 mounted therein. This insertion piece is further providedwith packing boxes 20 for the spindle 9.

iso

` being then independent o f the difference in.

The operation ofthe valve is as follows: The steam or the gas flows inthe direction indicated by the arrows, the rate of flow pressure beforeand behind the valve, in accordance with the description above. Theamount of fluid passing in the unit of time only depends on thevpressure before the valve and on the area of the passage, and inasmuch,as a rule, the pressure before the valve is constant or nearly so, thesaid amount of steam or gas may be adjusted to ,dierent values byaltering *the area of the v total area of passage is reduced.

It isobvious that a valve arranged in this manner is balanced so thatthere will be no more difliculties in operating the same, and it -willbe easy to adapt the valve as a regulating valve by causing a governorto directly or indirectly actuate the spindle 9 in some way or other.

A still more accurate control is obtained if, .on the plunger beingdisplaced up or down, the same is simultaneously turned, while it isalso provided with a flange uncovering only one nozzle at a time.

Such an embodiment is shown'in Fig. 7. Herein the nozzles provided inthe insertion piece are arranged along a helix, and the plunger- 18 isprovided with a flange 21.

` The helix, along which the nozzles are arn ere ranged, is made withthe same pitch as the thread of the spindle 9. Thus, if the hand wheel11 is turned, th'e plunger 18 will be turned at the same time therewithby rea` son of the thread of the spindle being displaced, and the flange21 opens or closes for one nozzle at a time. A overnor may be caused toactuate the spmdle 9, an exceedingly accurate control being attainedthereby.

lAnother embodiment of the invention is shown in Figs. 8 and 9, 'inwhich the stop member is not made as a plunger adapted to be displacedup and down, but as a rotatable slide 22.'H By turning this slide, agreater or lesser number of the passage openings provided in ltheinsertion piece 17, and sha ed aside Laval nozzles, are being covoruncovered.

Fig. 9 shows a section through the valve on line A-A. From this figureit will be seen how the. passage openings are arran ed in 'this casewith respect to the rotata le slide 22.

Finally, Fig. 10 shows an embodiment of the invention with two valvediscs 12, 12',

-the valve seats being so shaped that a nozzle placed so as to alter thearea ofthe passage.

What I claim as new and desire to secure by Letters Patent of thelUnited States of 1. A valve for use in steam systems where steam is tobe supplied from one conduit to a second conduit having a pressurehigher than 53 percent of the pressure in the first conduit, comprisingports, control members for said ports, a s indle connected to saidcontrol members, tie contour of said portsl and control members beingsuch as to forni a gradually expanding passageway in direction towardthe spindle and a second gradually expanding passageway in directionaway fromthe splndle.

2. A valve for use in steam systems where steam is to be sup lied fromone conduit to a second conduit aving a pressure higher than 53 percentof thepressure in the first conduit, comprising a pluralit of seats anda plurality of discs for sai seats, the discs and seats being sodesigned as to form a plurality of gradually expanding nozzles in theformof annuli. A

3. Agbalanced valve having a plurality of adjustable passages, saidpassages being in the form o nozzles of the de Laval nozzle type for allositions of adjustment of the` valve, mortier that the flow throu h thevalve may be independent of pressure y hind y the valve for angivenadjustment.

4. A balance valve comprising a plurality of ports, a control member foreach of said ports, a ls indle connected to said control members, tIliecontour of said ports and control members beingk such as to' provide aplurality of passages of the de Laval nozzle type for all positions ofthe spindle, in order that the flow through the valve may beindependentof the pressure behind the valve for any 'given position ofthe spindle. In testimony whereof I affix my signature.

JOHANNES RUTHS

